electrophoretic mobility

Ian A. York iayork at panix.com
Thu Aug 5 10:15:21 EST 1999

In article <7oc5ho$87s_001 at leeds.ac.uk>,
C.S. Wilding <BGYCSW at leeds.ac.uk> wrote:
>When electrophoresing (through 0.8% agarose in 1xTBE) some restriction 
>digested DNA samples, why do samples cut with EcoRI in NEB's Eco buffer 
>(50mM NaCl, 100mM Tris-HCl, 10mM MgCl2, 0.025% Triton X-100) "appear to 
>run slower" than uncut DNA or Eco cut in NEB buffer#2 (10mM Tris-HCl, 
>10mM MgCl2, 50mM NaCl, 1mM DTT). I say "appear to run slower" as this 

I assume it's because the salt concentration is different, allowing
different currents in the local area; the effect usually disappears before
the dye front migrates more than a few millimeters, which I assume is
because the salts have migrated further ahead and are no longer affecting
the current there.  The effect on the actual DNA bands is minimal, if you
let it run out a bit.  I suppose if you were using a really small gel it
might show some effect.

    Ian York   (iayork at panix.com)  <http://www.panix.com/~iayork/>
    "-but as he was a York, I am rather inclined to suppose him a
     very respectable Man." -Jane Austen, The History of England

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